Electronic apparatus, control method and program thereof, and battery for operating electronic apparatus

ABSTRACT

An electronic apparatus using a fuel cell as at least one electric power source. The fuel cell has an electric power output unit for outputting an electric power through a chemical reaction between fuel gas and oxidant gas, a purge device for purging the electric power output unit and a purge control unit for issuing a purge instruction to the purge device. The electronic apparatus has a monitor unit for monitoring a consumption power, an operation state or a manipulated state of the electronic apparatus, and a purge permission unit for judging from an output of the monitor unit whether the purge control unit is permitted to issue the purge instruction, and outputting a judgment result to the purge control unit.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 11/908,892,filed Sep. 17, 2007, which is the National Stage application under 35U.S.C. 371 of International Application No. PCT/JP2006/309977, filed May12, 2006, the entire disclosures of which are hereby incorporated byreference.

TECHNICAL FIELD

The present invention relates to an electronic apparatus capable ofusing a fuel cell as a power source, and its control method and program,and more particularly to an electronic apparatus mounting a fuel cellwhich recovers a power generation efficiency through purge, and itscontrol method and program.

BACKGROUND ART

Presently, there are many apparatus which can operate by a power supplyfrom a battery. Among these apparatus, an apparatus capable of beingused outdoors has a big issue of a battery life of power supply.

In the following, description will be made by referring to a digitalcamera as one example of electronic apparatus capable of being usedoutdoors.

In a generally known digital camera, an object image taken through aphotographing is photoelectrically converted by an image pickup deviceinto an image signal, the image signal is A/D converted and recorded ona recording medium, and an image can be displayed on a built-in liquidcrystal monitor.

Particularly, a single-lens reflex digital camera capable of exchanginga photographing is required to have a high quality of a photographedimage, a wide luminance range of an object capable of being photographedand the like, while a good manipulation performance and a high speedcontinuous photographing performance are also maintained similar to asilver salt film camera. It is therefore essential that a highsensitivity image pickup device which has a large number of pixels isadopted. In addition, as compared to a silver salt film camera, largescale electronic circuits using a number of electric components areadditionally used, including an image pickup circuit, an imageprocessing circuit, an image display circuit and the like. Therefore, aconsumption power becomes large and it is required to have a batterycapable of supplying a sufficient energy. While compactness andlightness of cameras advance, conventional primary and secondarybatteries are becoming difficult to supply cameras with a sufficientdrive energy.

In order to solve these problems, a compact fuel cell has been paidattention. In a fuel cell, fuel gas such as hydrogen as a reaction gasis electrochemically reacted with oxidant gas such as oxygen containedin an atmospheric air, to thereby convert chemical energy contained inthe fuel, directly into electric energy.

Next, description will be made on a power generation principle of a fuelcell. In a fuel cell, fuel gas containing hydrogen is supplied to a fuelelectrode and oxidant gas containing oxygen is supplied to an oxygenelectrode to thereby obtain an electromotive force throughelectrochemical reactions occurring between both the electrodes.Hydrogen supplied to the fuel electrode is separated by catalyst intoprotons and electrons. The separated electrons move to the oxygenelectrode via an outer circuit, whereas the protons move to the oxygenelectrode via a solid state polymer film. At the oxygen electrode,protons, electrons and oxygen are coupled to generate water and carbondioxide. In the following, the electrochemical reactions in the fuelcell are shown. A formula (1) indicates a reaction at the fuelelectrode, a formula (2) indicates a reaction at the oxygen electrode,and a formula (3) indicates a reaction in the whole battery.

H₂→2H⁺+2e ⁻  (1)

(½)O₂+2H⁺+2e ⁻→H₂O  (2)

H₂+(½)O₂→H₂O  (3)

Fuel batteries are classified into various types depending upon anelectrolyte difference and the like. One know type is a fuel cell whichuses a solid state polymer film as electrolyte. A solid state polymerelectrolyte type fuel cell can realize low cost, is easy to make compactand light, and has a high output density in view of a batteryperformance. From these reasons, the fuel cell of this type is desiredto be a drive electric power source not only for cameras, but also forportable electronic apparatus such as note type personal computers,mobile phones and PDAs. A stack cell type fuel cell has also beenproposed, having a structure that a plurality of power generation cellsand separators are alternately laminated.

FIG. 11 is a diagram showing a change in an output voltage of a fuelcell in use. FIG. 12 is a diagram showing a change in an output voltageof a fuel cell in use under purge. As a power is generated by a fuelcell for a long period of time, an output voltage lowers. This isbecause water generated by a reaction between hydrogen and oxygendiffuses in a reverse direction to the fuel electrode and reduces apower generation area, and in addition, gas unnecessary for powergeneration remains at the fuel electrode and lowers a hydrogen partialpressure. Since a fuel cell is used as a current supply source of anelectronic apparatus, it is not preferable that an output voltage lowersto an allowable voltage range of the electronic apparatus or more.

In order to solve this, generally a flow rate of hydrogen to be suppliedto the fuel electrode is increased instantly to discharge moisture andgas which are unnecessary for power generation and remain at the fuelelectrode, to an external of stack cells, so that a power generationarea is recovered and a hydrogen partial pressure is raised to therebystabilize an output voltage (a purge method). After purge, an outputvoltage of the fuel cell rises as shown in FIG. 12.

Several techniques have been disclosed as methods of judging the timingwhen a fuel cell is purged. According to one method, voltages of allstack cells constituting a fuel cell are detected, and when any onelayer of cells presents a predetermined voltage or lower, purge iseffected (for example, refer to JP-A-2002-093438). There are a method offorcibly effecting purge each time a predetermined time lapses (forexample, refer to JP-A-2000-215905) and a method of performing bothperiodical purge and hydrogen purge upon voltage measurement of eachcell (for example, refer to JP-A-2003-115314). Other methods include amethod (for example, refer to JP-A-2002-164065) of measuring voltage andcurrent output from a fuel cell for a predetermined period or by apredetermined number of samples, calculating an internal resistance fromthe measured value, comparing the internal resistance with a presetstandard value, and estimating the state of electrolyte of the fuel cellto effect purge when necessary.

However, although purge is effected to recover the power generationarea, raise the hydrogen partial pressure and stabilize the outputvoltage, an output voltage of the fuel cell lowers momentarily duringpurge because of air mixture to the fuel electrode by reverse diffusion,drop of hydrogen pressure and temperature in the fuel electrode. Aportable electronic apparatus such as a digital camera is required tohave a severe precision of management of a power source system. Forexample, if the timing when the fuel cell is purged is superposed uponthe timing when the electronic apparatus requires a relatively largepower, the power necessary for the electronic apparatus cannot be drawnfrom the fuel cell, and there arises a problem of an insufficient powerof the electronic apparatus.

If an electronic apparatus is remained unused for a long term, fuel gasleaks minutely from the fuel electrode of a fuel cell, so that ahydrogen concentration on the fuel electrode side falls. When the fuelcell is thereafter activated, there arises a problem that it takes along time to raise the output voltage to a necessary voltage.

DISCLOSURE OF THE INVENTION

The present invention has been made in consideration of the abovesituation, and has as its object to provide an electronic apparatuscapable of purging a fuel cell at an optimum timing suitable for theapparatus state, its control method and program, and a battery foroperating the electronic apparatus.

According to the present invention, the foregoing object is attained byproviding an electronic apparatus using, as at least one electric powersource, a fuel cell having an electric power output unit for outputtingan electric power through a chemical reaction between fuel gas andoxidant gas, a purge device for purging the electric power output unitand a purge control unit for issuing a purge instruction to the purgedevice, the electronic apparatus comprising: a monitor unit formonitoring a consumption power, an operation state or a manipulatedstate of the electronic apparatus; and a purge permission unit forjudging from an output of the monitor unit whether the purge controlunit is permitted to issue the purge instruction, and outputting ajudgment result to the purge control unit.

According to the present invention, the foregoing object is alsoattained by providing a control method for an electronic apparatususing, as at least one electric power source, a fuel cell having anelectric power output unit for outputting an electric power through achemical reaction between fuel gas and oxidant gas, a purge device forpurging the electric power output unit and a purge control unit forissuing a purge instruction to the purge device, the control methodcomprising steps of: monitoring a consumption power, an operation stateor a manipulated state of the electronic apparatus; judging from amonitor result by the monitoring step whether the purge control unit ispermitted to issue the purge instruction; and outputting a judgmentresult by the judging step to the purge control unit.

According to the present invention, the foregoing object is alsoattained by providing a fuel cell unit comprising: an electric poweroutput unit for outputting an electric power through a chemical reactionbetween fuel gas and oxidant gas; a purge device for purging theelectric power output unit; and a purge control unit for issuing a purgeinstruction to the purge device, in accordance with a permission signalfrom an electronic apparatus to be driven.

Other features and advantages of the present invention will be apparentfrom the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the presentinvention and, together with the description, serve to explain theprinciples of the invention.

FIG. 1 is comprised of FIGS. 1A and 1B are block diagrams showing theinternal structure of a single-lens reflex digital camera according toan embodiment of the present invention.

FIG. 2 is a block diagram showing an example of the internal structureof a fuel cell 80 mounted in the single-lens reflex digital camera shownin FIGS. 1A and 1B.

FIG. 3 is a flow chart illustrating a control operation for the fuelcell 80 of the single-lens reflex digital camera shown in FIGS. 1A, 1Band 2.

FIG. 4 is a diagram showing an example of a consumption power amount ofa drive sequence for a single-lens reflex digital camera.

FIG. 5 is a flow chart illustrating an example of the control operationfor the fuel cell 80 of a single-lens reflex digital camera in a firstuse state.

FIG. 6 is a flow chart illustrating an example of the control operationfor the fuel cell 80 of the single-lens reflex digital camera in asecond use state.

FIG. 7 is a flow chart illustrating an example of the control operationfor the fuel cell 80 of the single-lens reflex digital camera in a thirduse state.

FIG. 8 is a flow chart illustrating an example of the control operationfor the fuel cell 80 of the single-lens reflex digital camera in afourth use state.

FIG. 9 is a flow chart illustrating an example of the control operationfor the fuel cell 80 of the single-lens reflex digital camera in a fifthuse state.

FIG. 10 is a flow chart illustrating an example of another controloperation for the fuel cell 80 of the single-lens reflex digital camerain the fifth use state.

FIG. 11 is a diagram showing a change in an output voltage of a fuelcell in use.

FIG. 12 is a diagram showing a change in an output voltage of a fuelcell in use under purge.

FIG. 13 is comprised of FIGS. 13A and 13B are block diagrams showing theinternal structure of a cellar phone according to an embodiment of thepresent invention.

FIG. 14 is a flow chart illustrating the control operation of a fuelcell unit of the cellar phone shown in FIGS. 13A and 13B.

FIG. 15 is a flow chart illustrating the operation to be executed if itis judged at Step S802 shown in FIG. 14 that a sufficient amount ofhydrogen for abrupt hydrogen emission by purge does not exist in thehydrogen absorbing alloys 410 in the fuel tank 400.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described indetail in accordance with the accompanying drawings.

As a portable electronic apparatus adopting the present invention, asingle-lens reflex digital camera is referred to for describing thefollowing embodiments.

FIGS. 1A and 1B are block diagrams showing the internal structure of asingle-lens reflex digital camera according to an embodiment of thepresent invention.

As shown in FIGS. 1A and 1B, a single-lens reflex digital camera of theembodiment is constituted of: an electronic camera main body 100constituting the single-lens reflex digital camera main body; aphotographing unit 300 including a taking optical system constituted ofa plurality of photographing 310 and the like; recording media 200 and210; an electric power source unit 116; and a fuel tank (hydrogen supplysource unit) 400. The recording media 200 and 210, electric power sourceunit 116 and fuel tank 400 are detachably mounted on the single-lensreflex digital camera.

The photographing unit 300 includes a drive unit for driving thephotographing 310, light amount limiting means for adjusting an amountof incidence light beams transmitted through the photographing 310, andthe like. The photographing unit 300 is detachably mounted on the cameramain body 100.

The camera main body 100 is structured in the following manner.

Reference numeral 12 denotes a shutter for controlling an exposureamount of an image pickup device 14. The image pickup device 14 convertsan optical image into an electric signal, and is, for example, a CCDsensor. A light beam incident upon the photographing 310 is directed byan iris 312 as light amount limiting means, lens mounts 306 and 106, amirror 122 and the shutter 12, and focused as an optical image on animage pickup plane of the image pickup device 14.

The light beam incident upon the image pickup lenses 310 is directed toan optical finder 110 by the mirrors 122 and 124. The mirror 122 may beof a quick return mirror structure or of a half mirror structure.

Reference numeral 16 denotes an A/D converter for converting an analogsignal output from the image pickup device 14 into a digital signal(hereinafter called image data). Reference numeral 18 denotes a timinggenerator circuit for supplying the image pickup device 14, A/Dconverter 16 and a D/A converter 26 with a clock signal and a controlsignal, the timing generator circuit being controlled by a memorycontrol circuit 22 and a system control circuit 50.

Reference numeral 20 denotes an image processing circuit for effecting apredetermined pixel interpolation process and color conversion processfor image data from the A/D converter 16 and image data from the memorycontrol circuit 22. In the image processing circuit 20, a predeterminedcalculation process is effected by using image data when necessary, andin accordance with the calculation result, the system control circuit 50effects a through-the-lens (TTL) type auto focus (AF) process for adistance measurement unit 42 and a photometry unit 44, an automaticexposure (AE) control process and an electronic flash (EF) process. Theimage processing circuit 20 further effects a white balance (WB) processin accordance with the calculation result in a white balance controlcircuit 46.

The memory control circuit 22 controls the A/D converter 16, the timinggenerator circuit 18, the image processing circuit 20, an image displaymemory 24, the D/A converter 26, a memory 10, and acompression/expansion circuit 32. Image data output from the A/Dconverter 16 is written into the image display memory 24 or memory 30via the image processing circuit 20 and memory control circuit 22 or viaonly the memory control circuit 22.

The image display memory 24, the D/A converter 26 and an image displayunit 28 as a TFT/LCD for example, effect an image display process. Morespecifically, display image data written in the image display memory 24is output to and displayed on the image display unit 28 via the D/Aconverter 26. If image data photographed with the image pickup device 14is sequentially displayed on the image display unit 28, an electronicview finder function can be realized. The image display unit 28 can turnon/off a display as desired in accordance with an instruction from thesystem control unit 50. When a display is turned off, a consumptionpower of the electronic camera main body 100 can be reducedconsiderably.

The memory 30 is a storage medium for storing photographed still imagesand moving images, and has a capacity sufficient for storing apredetermined number of still images, and moving images for apredetermined time. Therefore, even in continuously photographing aplurality of still images and in panorama photographing, high speed andlarge capacity image write is executed relative to the memory 30. Thememory 30 can be used as a working area of the system control circuit50.

The compression/expansion circuit 32 compresses and expands image datathrough adaptive discrete cosine transform (ADCT) or the like. Thecompression/expansion circuit 32 reads image data stored in the memory30, executes the compression or expansion process, and writes theprocessed image data into the memory 30.

Reference numeral 40 denotes a shutter control circuit for controllingthe shutter 12 in accordance with photometry information from thephotometry unit 44, in corporation with an iris control circuit 340 forcontrolling an iris 312. The distance measurement unit 42 executes theauto focus (AF) process. The distance measurement unit can measure anin-focus state of an image focused as an optical image, by making alight beam incident upon the lenses 310 enter the distance measurementunit 42 via the iris 312, lens mounts 306 and 106, mirror 122 and adistance measurement sub-mirror (not shown).

The photometry unit 44 executes the automatic exposure (AE) process. Thephotometry unit can measure an exposure state of an image focused as anoptical image, by making a light beam incident upon the lenses 310 enterthe photometry unit 44 via the iris 312, lens mounts 306 and 106, mirror122 and a photometry lens (not shown).

Reference numeral 45 denotes a white balance calculation circuit forcalculating a color temperature by using image data of an imagephotographed with a TTL method. The white balance control circuit 46calculates white balance correction data necessary for the imageprocessing circuit 20 to execute the white balance process, inaccordance with a gain or the like for white balance adjustment presetin accordance with a light source selection and a color temperatureinput by a photographer.

Reference numeral 48 denotes an electronic flash having a projectionfunction for AF supplementary light and an electronic flash lightmodulation function. In accordance with calculation results, by theimage processing circuit 20, of image data of an image photographed withthe image pickup device 14, the system control circuit 50 controls theshutter control circuit 40, the iris control circuit 340 and a distancemeasurement control circuit 342. Exposure control and auto focus (AF)control can be made by using a video TTL method. The auto focus (AF)control may be made by using both the measurement results of thedistance measurement unit 42 and calculation results in the imageprocessing circuit 20 of image data of an image photographed with theimage pickup device 14. The exposure control may be made by using boththe measurement results of the photometry unit 44 and calculationresults in the image processing circuit of image data of an imagephotographed with the image pickup device 14.

Reference numeral 50 denotes a system control circuit for controllingthe entirety of the electronic camera main body 100, and referencenumeral 52 denotes a memory for storing operation constants, variablesand programs for the system control circuit 50.

Reference numeral 54 denotes a display unit having a display functionof, for example, a liquid crystal display for displaying an operationstate and a message by using characters, images, sounds and the like anda sound reproducing function of, for example, a speaker for reproducingan operation sound and an alarm sound, in accordance with the executionof a program in the system control circuit 50. One or a plurality ofdisplay units 54 are mounted at positions easy to view such as positionsnear an operation unit of the electronic camera main body 100. Forexample, the display units are constituted of LCDs, LEDs, soundgenerator devices and the like.

Operation means for the single-lens reflex digital camera will bedescribed specifically. Of the display contents on the display unit 54,displays on LCD or the like include: a single shot—continuousphotographing display; a self timer display; a compression factordisplay; a record pixel number display; a record photograph frame numberdisplay; a remaining photograph frame number display; a shutter speeddisplay; an iris value display; an exposure correction display; a flashdisplay; a red-eye relax display; a macro photographing display; abuzzer setting display; a remaining clock battery capacity display; aremaining battery capacity display; an error display; an informationdisplay by a plurality of digits of numerical values; an attach anddetach state display for the recording media 200 and 210; an attach anddetach state display for the photographing unit 300; a communication I/Foperation display; a date and time display; a connection state displayfor an external computer; and other displays.

Of display contents on the display unit 54, displays on the opticalfinder 110 include: an in-focus display; a photographing preparationcomplete display; a hand shaking alarm display; a flash charge display;a flash charge complete display; a shutter speed display; an iris valuedisplay; an exposure correction display; a record medium write operationdisplay; and other displays. Of display contents on the display unit 54,displays on LED or the like include: an in-focus display; aphotographing preparation complete display; a hand shaking alarmdisplay; a flash charge display; a flash charge complete display; arecord medium write operation display; a macro photographing settingnotice display; a secondary battery charge state display; and otherdisplays. Of display contents on the display unit 54, displays on a lampor the like include a self timer notice display. A self timer noticelamp may be used as an AF supplementary light source.

Reference numeral 55 denotes a purge alarm unit for alarming a user tooperate a purge operation switch 78 when an output voltage of the fuelcell 80 lowers and purge becomes necessary. The details will be laterdescribed. Purge means a method of increasing rapidly a flow rate ofhydrogen to be supplied to the fuel electrode of a fuel cell, anddischarging moisture and unnecessary gas remaining at the fuel electrodeto an external of stack cells to thereby recover the power generationarea and raise the hydrogen partial pressure.

Reference numeral 56 denotes an electrically erasable and recordablenonvolatile memory for recording the contents in the memory 52 whennecessary. For example, the nonvolatile memory is an EEPROM or the like.A mode dial 60, a release switch SW1 62, a release switch SW2 64 and awhite balance select switch 66 constitute operation means for inputtingvarious operation instructions for the system control circuit 50. Theoperation means is constituted of a single or a plurality ofcombinations of a switch, a dial, a touch panel, a pointing device forline-of-view detection, a voice recognition apparatus and the like.

The operation means will be described specifically. The mode dial 60 isa rotary switch capable of changing over various photographing modesincluding: an automatic photographing mode; a program photographingmode; a shutter speed priority photographing mode; an iris priorityphotographing mode; a manual photographing mode; a focal depth priority(depth) photographing mode; a portrait photographing mode; a scenephotographing mode; a close-up photographing mode; a sport photographingmode; a night scene photographing mode; a panorama photographing mode;and the like.

The release switch SW1 62 turns on at the intermediate state ofdepressing a release button (not shown) to instruct a start of theoperation of the auto focus (AF) process, an automatic exposure (AE)process, a white balance (WB) process, an electronic flash (EF) processand the like. The release switch SW2 64 turns on at the completion stateof depressing the release button (not shown) to instruct a start of aseries of processes including an exposure process of writing image dataread from the image pickup device 12 into the memory 30 via the A/Dconverter 16 and memory control circuit 22, a development process usingcalculations by the image processing circuit 20 and memory controlcircuit 22, and a record process of reading image data from the memory30, compressing the image data at the compression/expansion circuit 32,and writing the image data in the recording medium 200 or 210.

Reference numeral 70 denotes an operation unit constituted of variousbuttons, touch panels and the like. For example, the operation unit isconstituted of a menu button, a set button, a macro button, amulti-screen reproduction change-over page button, a flash settingbutton, a single shot—continuous photographing—self timer change button,a menu shift plus (+) button, a menu shift minus (−) button, aphotographing image quality select button, an exposure correctionbutton, a date and time setting button, a select and change-over button,a decision and execution button, an image display on/off switch, a quickreview on/off switch, a compression mode switch, a reproduction switch,an AF mode setting switch, a white balance select switch and the like.

The select and change-over button is used for setting a selection or achange of various functions when photographing and reproduction in apanorama mode are effected. The decision and execution button is usedfor setting a decision and execution of various functions whenphotographing and reproduction in a panorama mode are effected. Theimage display on/off switch is used for turning on/off the image displayunit 28. The quick review on/off switch is used for setting a quickreview function of automatically reproducing image data of an imageimmediately after photographing. The compression mode switch is used forselecting a compression factor of JPEG compression or for selecting aCCD/RAW mode for digitalizing directly image data output from the imagepickup device and recording the image data in the recording medium.

The reproduction switch can set various functional modes including areproduction mode, a photographing state defective image reproductionmode, a PC connection mode and the like. The AF mode setting switch canset a one-shot AF mode in which an auto focus operation is stopped oncewhen the release switch SW1 62 is depressed and an in-focus state ismaintained if an in-focus state is obtained, and a servo AF mode inwhich an auto focus operation continues while the release switch SW1 62is depressed.

The white balance select switch is used for selecting an auto whitebalance and a manual white balance. In the auto white balance, a colorof external light is calculated from the output signal of the imagepickup device 14, and the white balance is adjusted by a TTL methodusing color temperature data. In the manual white balance, aphotographer judges the type (e.g., sun light, electric bulb,fluorescent lamp or the like) of a light source in a photographingenvironment, selects the type of the light source by using a lightsource select button (not shown), or the photographer measures a colorhue (color temperature) of the photographing environment, inputs a colortemperature of the photographing environment into the electronic cameraby using a color temperature input button, and the gains of a red signalinput circuit and a blue signal input circuits are set to the presetfixed gains specific to the light source and color temperature, inaccordance with selection of the light source and input of the colortemperature.

If the plus button and minus button are provided with a rotary dialswitch, the functions and numerical values of the buttons can be moresmoothly selected.

Reference numeral 72 denotes an electric power switch which can switchbetween a power-on and power-off of the electronic camera main body 100.It is also possible to switch between a power-on and power-off ofvarious components connected to the electronic camera main body 100including the photographing unit 300, an external electronic flash, therecording media 200 and 210, and the like. Reference numeral 74 denotesa fuel tank attach and detach detection unit for detecting whether thefuel tank 400 is attached to a connector 93.

Reference numeral 76 denotes a drive electric power detection circuitfor detecting a drive electric power for the electronic camera main body100. Reference numeral 78 denotes a purge operation switch. When thisswitch is turned on, the system control circuit 50 controls the fuelcell 80 to effect purge. The detailed structure of the fuel cell 80 willbe later given.

The fuel cell 80 supplies an electric power to the electronic cameramain body 100. Reference numerals 93 and 412 denote connectors forconnecting the electronic camera main body 100 and a fuel tank 400 forstoring fuel gas (hydrogen) of the fuel cell 80. Reference numeral 94denotes a suction port for sending air to the oxygen electrode (notshown) of the fuel cell 80. Reference numeral 96 denotes an exhaust portfor discharging hydrogen and impurities and the air used in the fuelcell 80 from the electronic camera main body 100 to an external, whenpurge of the fuel cell is effected. Reference numeral 97 denotes anelectric power source change-over unit for switching the electric powersource of the electronic camera main body 100 from the fuel cell 80 tothe electric power source unit 116, or from the electric power sourceunit 116 to the fuel cell 80, under the control of the system controlcircuit 50.

Reference numeral 98 denotes an electric power source control circuitwhich is constituted of a battery detection circuit, a DC/DC converter,switch circuit for switching between blocks to be supplied with anelectric power. The electric power source control circuit detects thetype of a battery and a remaining battery capacity, controls the DC/DCconverter in accordance with the detection results or an instructionfrom the system control circuit 50, and supplies a necessary voltage toeach component including the recording media during a necessary period.Reference numerals 112 and 114 denote connectors for connecting theelectronic camera main body 100 and electric power source unit 116. Theelectric power source unit 116 is constituted of a primary battery suchas an alkali battery and a lithium battery, a secondary battery such asa NiCd battery, an NiMH battery and a Li battery, an AC adapter and thelike.

Reference numerals 91 and 95 denote interfaces with the recording mediasuch as a memory card and a hard disc. Reference numerals 92 and 99denote connectors for connection of the recording media such as a memorycard and a hard disc. Reference numeral 118 denotes a recording mediaattach and detach detection unit for detecting whether the recordingmedium 200 or 210 is connected to the connectors 92 and 99. In thisembodiment, description will be made assuming that two series ofinterfaces and connectors are provided for mounting the recording media.A single or a plurality of series may be used obviously for theinterfaces and connectors for mounting the recording media. Acombination of interfaces and connectors having different specificationsmay also be used.

The specifications of the interfaces and connectors may be those inconformity with the specifications of PCMCIA cards, CF (compact flash)cards or the like. If the interfaces 91 and 95 and connectors 92 and 99are in conformity with the specifications of PCMCIA cards or CF (compactflash) cards and if various communication cards such as LAN cards, modemcards, USB cards, IEEE1394 cards, P1284 cards, SCSI cards and PHS cardsare used, then image data and management information added to the imagedata can be transferred to and from other computers and peripheralapparatus such as printers.

Reference numeral 136 denotes a communication unit having variouscommunication functions such as RS232, USB, IEEE1394, P1284, SCSI,modems, LAN and wireless communications. Reference numeral 138 denotes aconnector for connecting the electronic camera main body 100 to anotherapparatus via the communication unit 136, or an antenna for wirelesscommunications.

Reference numeral 140 denotes an interface for connecting the electroniccamera main body 100 to the photographing unit 300 in the lens mount106. Reference numeral 142 denotes a connector for electricallyconnecting the electronic camera main body 100 to the photographing unit300. Reference numeral 144 denotes a lens attach and detach detectionunit for detecting whether the photographing unit 300 is attached to thelens mount 106 and/or connector 142.

The connector 142 has a function of transferring a control signal, astate signal, a data signal and the like between the electronic cameramain body 100 and photographing unit 300 and supplying various voltagesand currents. The connector 142 may provide not only the electriccommunications but also optical communications and audio communications.

Reference numeral 200 denotes a recording medium such as a memory cardand a hard disc. The recording medium 200 is constituted of a recordingarea 202 made of a semiconductor memory, a magnetic disk or the like, aninterface 204 with the electronic camera main body 100, and a connector206 for connection to the electronic camera main body 100.

Reference numeral 210 denotes a recording medium such as a memory cardand a hard disc. The recording medium 210 is constituted of a recordingarea 212 made of a semiconductor memory, a magnetic disk or the like, aninterface 214 with the electronic camera main body 100, and a connector216 for connection to the electronic camera main body 100.

The above-described photographing unit 300 will be described in moredetail. As described above, the photographing unit 300 is of a lensexchangeable type.

The lens mount 306 mechanically couples the photographing unit 300 tothe electronic camera main body 100. The lens mount 306 has variousfunctions of electrically connecting the photographing unit 300 to theelectronic camera main body 100.

Reference numeral 320 denotes an interface for connection of thephotographing unit 300 to the electronic camera main body 100 in thelens mount 306. Reference numeral 322 denotes a connector forelectrically connecting the photographing unit 300 to the electroniccamera main body 100. The connector 322 has a function of transferring acontrol signal, a state signal, a data signal and the like between theelectronic camera main body 100 and photographing unit 300 and supplyingor being supplied with various voltages and currents. The connector 322may provide not only the electric communications but also opticalcommunications and audio communications.

The iris control circuit 340 controls the iris 312 in accordance withphotometry information supplied from the photometry unit 44, incorporation with the shutter control circuit 40 for controlling theshutter 12. The distance measurement control circuit 342 controlsfocusing of the photographing 310. The zoom control circuit 346 controlsthe whole of the photographing unit 300. The lens system control circuit346 provides a memory function of storing operation constants,variables, programs and the like and a nonvolatile memory function ofstoring identification information on a number specific to thephotographing unit 300, management information, and functionalinformation such as an open iris value, a minimum iris value, a focaldistance and the like, various present and past setting values and thelike.

Next, the details of the fuel tank 400 will be described. The fuel tank400 is constituted of hydrogen absorbing alloy 410 and a connector 412.The hydrogen absorbing alloy 410 contains fuel gas (hydrogen) necessaryfor driving the fuel cell 80. The connector 412 connects the fuel tank400 to the electronic camera main body 100. The hydrogen absorbing alloy410 adjusts a hydrogen pressure in the fuel cell to be always constant,and sends fuel gas (hydrogen) to the fuel cell 80 via the connectors 93and 412.

Next, description will be made on the structure of the fuel cell 80mounted on the electronic camera main body 100 shown in FIGS. 1A and 1B.FIG. 2 is a block diagram showing an example of the internal structureof the fuel cell 80 mounted on the single-lens reflex digital camerashown in FIGS. 1A and 1B. In FIG. 2, identical reference numerals tothose shown in FIGS. 1A and 1B indicate the components having similarfunctions.

In FIG. 2, reference numeral 81 denotes a fuel cell stack constituted ofa plurality of cells. Reference numeral 82 denotes a compressor forcompressing air sucked from the suction port 94 and sending thecompressed air to the oxygen electrode (not shown) of the fuel cellstack 81. Reference numeral 83 denotes a purge valve as purge means fordischarging circulating hydrogen to an external of the electronic cameramain body 100 via the exhaust port 96, and discharging water andimpurities accumulated in the fuel cell stack 81 to thereby effectpurge.

Reference numeral 84 denotes an ejector for circulating fuel gas(hydrogen) discharged from the fuel cell stack 81. Reference numeral 85denotes a sensor for measuring a pressure of the oxidant gas (air).Reference numeral 86 denotes a sensor for measuring a pressure of thefuel gas (hydrogen). Reference numeral 87 denotes a sensor for measuringa flow rate of the oxidant gas. Reference numeral 88 denotes a sensorfor measuring a flow rate of the fuel gas (hydrogen).

Reference numeral 89 denotes a cell voltage detection circuit formeasuring a voltage of each cell in the fuel cell stack 81. Althoughonly one cell voltage detection circuit 89 is shown in FIG. 2 for thepurposes of simplicity, the cell voltage detection circuit is providedfor each cell or for each cell group in the fuel cell stack 81. It isdesired to detect a cell voltage in this manner when an output of thefuel cell is measured. A voltage detection circuit may be provided tomeasure an output voltage on the electronic apparatus side.

Reference numeral 90 denotes a fuel cell system control circuit forcontrolling the compressor 82 and the like to obtain a target electricpower amount, in accordance with an input pressure and flow rate of thefuel gas (hydrogen) and an input pressure and flow rate of the oxidantgas (air). An output of the cell voltage detection circuit 89 is sent tothe system control circuit 50 of the electronic camera main body 100,and when a purge instruction is received from the system control circuit50, purge is effected by driving the purge valve 83 as purge controlmeans.

Next, description will be made on the control operation for the fuelcell 80 of the single-lens reflex digital camera shown in FIGS. 1A, 1Band 2.

FIG. 3 is a flow chart illustrating the control operation for the fuelcell 80 of the single-lens reflex digital camera shown in FIGS. 1A, 1Band 2. shown in FIG. 3, first, while the electronic camera main body 100is driven by using the fuel cell 80 as electric power supply means, thefuel cell system control circuit 90 makes the cell voltage detectioncircuit 89 measure a cell voltage of the fuel cell stack 81, and it isjudged whether the cell voltage is lower than a first predeterminedvalue necessary for purge (Step S101).

If it is judged that the cell voltage is higher than the firstpredetermined value (NO at Step S101), the flow returns to Step 101whereat the fuel cell system control circuit 90 makes the cell voltagedetection circuit 89 measures a cell voltage of the fuel cell stack 81.Step S101 is repeated until the cell voltage becomes lower than thefirst predetermined value.

If it is judged that the cell voltage is lower than the firstpredetermined value (YES at Step S101), the fuel cell system controlcircuit 90 notifies the system control circuit 50 of that the cellvoltage became lower than the first predetermined value and purge isnecessary (Step S102). The system control circuit 50 judges from adetection result of the drive electric power detection circuit 76whether a drive electric power of the electronic camera main body 100 islower than a predetermined value (Step S103). This predetermined valueis set to a level at which the operation of the electronic camera mainbody 100 is not influenced even if a voltage drop occurs during purge.

The predetermined value at Step S103 will be described with reference toFIG. 4. FIG. 4 is a diagram showing an example of a consumption poweramount during a drive sequence of the single-lens reflex digital camera.As shown in FIG. 4, while the electric power switch 72 of thesingle-lens reflex digital camera is turned on, the consumption power ofthe camera circuit is always about 6.0 to 7.0 W. Depending upon thetiming of the camera drive sequence, a power of about 1.5 W is consumedby a motor (not shown) for driving the shutter 12, mirrors 122 and 124,and a power of about 4.0 W is consumed for driving the iris 312.

For example, if purge is effected while a consumption power isrelatively large (in FIG. 4, smaller than about 12.0 W) such as drivingthe motor (not shown) and iris 312 at the same time, a necessaryelectric power cannot be obtained because of an instantaneous voltagedrop, and there is a possibility that driving the single-lens reflexdigital camera is influenced. In order to avoid this, it is sufficientif purge is effected while the electric power is consumed only by thecamera circuit. Step S103 shown in FIG. 3 judges whether the electricpower consumed by the single-lens reflex digital camera is relativelysmall at the present time. In the example shown in FIG. 4, thepredetermined value at Step S103 shown in FIG. 4 is most preferablyabout 7.0 W indicated by a dotted line in FIG. 4.

If the drive electric power detection circuit 76 judges that the driveelectric power is smaller than the predetermined value (YES at StepS103), the system control circuit 50 outputs a purge start signal to thefuel cell system control circuit 90. The fuel cell system controlcircuit 90 drives the purge valve 83 to effect purge, and dischargesexcessive moisture and impurities in the fuel cell stack to the externalof the electronic camera main body 100 via the exhaust port 96 (StepS104).

If the drive electric power detection circuit 76 judges that the driveelectric power is larger than the predetermined value (NO at Step S103),the system control circuit 50 outputs a purge standby signal to the fuelcell system control circuit 90. The fuel cell system control circuit 90makes the cell voltage detection circuit 89 measure again the cellvoltage of the fuel cell stack 81 to judge whether the cell voltage islower than a second predetermined value. The second predetermined valueis lower than the first predetermined value, and is set to a value nearto an inhibition voltage (a voltage at which the single-lens reflexdigital camera cannot operate correctly) of the electronic camera mainbody 100.

If it is judged that the cell voltage is higher than the secondpredetermined value (NO at Step S105), the fuel cell system controlcircuit 90 outputs a judgment result to the system control circuit 50 toreturn to Step S103 whereat the system control circuit 50 makes thedrive electric power detection circuit 76 measure again the driveelectric power of the electronic camera main body 100. Namely, a loop ofStep S103 and S105 is executed if the detection result by the driveelectric power detection circuit 76 is larger than the predeterminedvalue and the cell voltage is higher than the second predeterminedvalue.

If it is judged that the cell voltage is lower than the secondpredetermined value (YES at Step S105), the fuel cell system controlcircuit 90 outputs a judgment result to the system control circuit 50 toadvance to Step S106 whereat the system control circuit 50 controls theelectric power source change-over unit 97 to change the electric powersource of the electronic camera main body 100 from the fuel cell 80 tothe electric power source unit 116.

Next, the system control circuit 50 outputs a purge start signal to thefuel cell system control circuit 90. The fuel cell system controlcircuit 90 drives the purge valve 83 to effect purge, and dischargesexcessive moisture and impurities in the fuel cell stack to the externalof the electronic camera main body 100 via the exhaust port 96. Duringpurge, in order to maintain the hydrogen pressure in the fuel cell stack81 at a predetermined value, hydrogen is always exhausted from thehydrogen absorbing alloy 410 in the fuel tank 400 and sent to the fuelcell 80 via the connectors 93 and 412 (Step S107).

After purge, the system control circuit 50 controls the electric powersource change-over unit 97 to change the electric power source of theelectronic camera main body 100 from the electric power source unit 116to the fuel cell 80 (Step S108).

A series of control operations of the fuel cell 80 has been describedabove. The processes shown in FIG. 3 are repeated while the single-lensreflex digital camera uses the fuel cell 80 as its electric powersource.

As described above, according to the single-lens reflex digital cameraof this embodiment, purge can be effected in the sequence of thesingle-lens reflex digital camera, if a necessary power is small. It istherefore possible to prevent battery shortage of the single-lens reflexdigital camera to be caused by a voltage drop during purge. It istherefore possible to drive the single-lens reflex digital camera by thefuel cell 80, by repeating purge without influencing the operation ofthe single-lens reflex digital camera.

Further, in the sequence of the single-lens reflex digital camera, theelectric power source unit 116 is temporality used in place of the fuelcell 80 and purge is completed during this period, if a necessaryelectric power is large and if purge is required immediately in thestate that driving the single-lens reflex digital camera is influencedif purge is effected. Accordingly, the fuel cell 80 can be purgedwithout influencing the operation of the single-lens reflex digitalcamera, and driving the single-lens reflex digital camera can continueby using the fuel cell 80 as the main electric power source.

Next, with reference to the accompanying drawings, description will bemade on examples of the control operation for the fuel cell 80 invarious use states (first to six use states) of the single-lens reflexdigital camera of this embodiment.

First Use State

The electric power switch 72 of the single-lens reflex digital camera isturned on in the first use state that the fuel gas of the fuel electrodein the fuel cell 80 was reduced because the single-lens reflex digitalcamera was maintained unused for a long time and the fuel cell 80 wasnot driven. FIG. 5 is a flow chart illustrating an example of thecontrol operation for the fuel cell 80 of the single-lens reflex digitalcamera in the first use state.

As shown in FIG. 5, first the system control circuit 50 judges whetherthe electric power switch 72 of the electronic camera main body 100 isturned on (Step S201). If it is judged that the electric power switch 72is off (NO at Step S201), the system control circuit 50 repeats thejudgment process at Step S201 until the electric power switch 72 isturned on.

In the state that the electric power switch 72 is OFF, an electric poweris not supplied to the single-lens reflex digital camera, so that thejudgment process is not performed. When the electric power switch 72changes from the OFF state to an ON state, an electric power is suppliedto the system control circuit 50 to judge the state of the electricpower switch. However, depending upon the control of the electric powersource, a power saving mode such as a suspend (sleeve) state isexecuted. In this case, the state of the electric power switch 72 isjudged as the OFF state. In this power saving mode, the judgment process(Step S201) can be executed at a predetermined time interval. In thispower saving mode, the ON state occurs upon a predetermined operation,e.g., in response to a photographing instruction. At this timing, the ONstate of the electric power switch 72 may be judged.

If it is judged that the electric power switch 72 is turned on (YES atStep S201), the system control circuit 50 starts driving the fuel cell80 (Step S202).

As the fuel cell 80 starts being driven at Step S202, the system controlcircuit 50 outputs a purge start signal to the fuel cell system controlcircuit 90. The fuel cell system control circuit 90 drives the purgevalve 83 to effect purge, and discharges excessive moisture andimpurities in the fuel cell stack 81 to the external of the electroniccamera main body 100 via the exhaust port 96.

During purge, in order to maintain the hydrogen pressure in the fuelcell stack 81 at a predetermined value, hydrogen is always exhaustedfrom the hydrogen absorbing alloy 410 in the fuel tank 400 and sent tothe fuel cell 80 via the connectors 93 and 412 (Step S203). At the sametime, the system control circuit 50 starts an electric power supply fromthe fuel cell 80 to the electronic camera main body 100 to activate thecamera (Step S204).

Whether the system control circuit 50 outputs the purge start signal tothe fuel cell system control circuit 90 at Step S202, may be determinedin the following manner. As described with Steps S101 and S102 in FIG.3, the cell voltage detection circuit 89 measures the cell voltage ofthe fuel cell stack 81, and in accordance with this measurement, thefuel cell system control circuit 90 notifies the system control circuitof that purge is necessary.

As described above, according to the single-lens reflex digital cameraof this embodiment, even if the fuel gas of the fuel electrode in thefuel cell 80 is reduced because the single-lens reflex digital camera ismaintained unused for a long time, purge is effected when the electricpower switch 72 of the single-lens reflex digital camera is turned on.It is therefore possible to fill the fuel electrode of the fuel cell 80with fuel gas and improve a rise of the output voltage. If purge iseffected only when necessary, wasteful purge can be avoided in the casein which the electric power switch is turned on and off in a short time.

Second Use State

The fuel tank 400 (fuel gas supply means) of the single-lens reflexdigital camera is loaded in the second use state that the fuel gas ofthe fuel electrode of the fuel cell 80 was reduced because the fuel tank400 was not loaded. FIG. 6 is a flow chart illustrating an example ofthe control operation for the fuel cell 80 of the single-lens reflexdigital camera in the second use state.

As shown in FIG. 6, even if the fuel tank 400 is not loaded in theelectronic camera main body 100, the system control circuit operates bythe electric power supplied from the electric power source unit 116. Thesystem control circuit 50 controls the fuel tank attach and detachdetection unit 74 to judge whether the fuel tank 400 is attached to theconnector 93 (Step S301).

If the fuel tank 400 is not mounted on the connector 93 (NO at StepS301), the fuel tank attach and detach detection unit 74 repeats thisjudgment until the fuel tank 400 is mounted on the connector 93.

If it is judged that the fuel tank 400 is mounted on the connector 93(YES at Step S301), the fuel tank attach and detach detection unit 74outputs a signal to the system control circuit 50, the signal beingdenotative of that the fuel tank 400 is loaded. The system controlcircuit 50 instructs the electric power source change-over unit 97 tochange the electric power source from the electric power source unit 116to the fuel cell 80 (Step S302).

Next, the system control circuit 50 outputs a purge start signal to thefuel cell system control circuit 90. The fuel cell system controlcircuit 90 drives the purge valve 83 to effect purge, and dischargesexcessive moisture and impurities in the fuel cell stack 81 to theexternal of the electronic camera main body 100 via the exhaust port 96.During purge, in order to maintain the hydrogen pressure in the fuelcell stack 81 at a predetermined value, hydrogen is always exhaustedfrom the hydrogen absorbing alloy 410 in the fuel tank 400 and sent tothe fuel cell 80 via the connectors 93 and 412 (Step S303).

Although the change-over of the electric power source is executed atStep S302 shown in FIG. 6, the change-over may be executed after purgeis effected (Step S303) and an output of the fuel cell 80 is stabilized.Whether the system control circuit 50 outputs the purge start signal tothe fuel cell system control circuit 90 at Step S303, may be determinedbased on the following fact. As described with Steps S101 and S102 inFIG. 3, the cell voltage detection circuit 89 measures the cell voltageof the fuel cell stack 81, and in accordance with this measurement, thefuel cell system control circuit 90 notifies the system control circuitof that purge is necessary, or not.

As described above, according to the single-lens reflex digital cameraof this embodiment, even if the fuel gas of the fuel electrode in thefuel cell 80 is reduced because the fuel tank 400 is not loaded in thesingle-lens reflex digital camera, purge is effected when the fuel tank400 is loaded. It is therefore possible to fill the fuel electrode ofthe fuel cell 80 with fuel gas and improve a rise of the output voltage.If purge is effected only when necessary, wasteful purge can be avoidedin the case in which the fuel tank 400 is exchanged instantly.

Third Use State

An auto power-off is effected in the third use state that the fuel gasof the fuel electrode in the fuel cell 80 was reduced because thesingle-lens reflex digital camera was maintained unused for a long timeand the fuel cell 80 was not driven. FIG. 7 is a flow chart illustratingan example of the control operation for the fuel cell 80 of thesingle-lens reflex digital camera in the third use state.

As shown in FIG. 7, first the system control circuit 50 judges whetherthe electric power switch 72 of the electronic camera main body 100 isturned on (Step S401). If the electric power switch 72 is turned on (YESat Step S401), the system control circuit 50 starts driving the fuelcell 80 to activate the single-lens reflex digital camera (Step S402).If the electric power switch 72 is in an OFF state (NO at Step S401),the system control circuit 50 repeats the judgment process until theelectric power switch 72 is turned on.

In the state that the electric power switch 72 is OFF, an electric poweris not supplied to the single-lens reflex digital camera, so that thejudgment process is not performed. When the electric power switch 72changes from the OFF state to an ON state, an electric power is suppliedto the system control circuit 50 to judge the state of the electricpower switch. However, depending upon the control of the electric powersource, a power saving mode such as a suspend (sleeve) state isexecuted. In this case, the state of the electric power switch 72 isjudged as the OFF state. In this power saving mode, the judgment process(Step S401) can be executed at a predetermined time interval. In thispower saving mode, the ON state occurs upon a predetermined operation,e.g., in response to a photographing instruction. At this timing, the ONstate of the electric power switch 72 may be judged.

Next, after the single-lens reflex digital camera is activated, thesystem control circuit 50 controls the timing generator circuit 18 tomeasure the time from when various switches of the operation unit 70 andthe like are lastly operated to the present time, to thereby judgewhether the unoperated state (hereinafter called a camera unoperatedstate) of the single-lens reflex digital camera reaches a predeterminedtime (Step S403).

If it is judged at Step S403 that the camera unoperated time does notreach the predetermined time (NO at Step S403), the system controlcircuit 50 repetitively measures the time from when various switches ofthe operation unit 70 and the like are lastly operated to the presenttime, until it is judged that the camera unoperated state is longer thanthe predetermined time. The single-lens reflex digital camera of thisembodiment has an auto power-off function of stopping an electric powersupply to the electronic camera main body 100 when the camera unoperatedstate continues longer than the predetermined time.

If it is judged at Step S403 that the camera unoperated state reachesthe predetermined time (YES at Step S403), the system control circuit 50outputs a purge start signal to the fuel cell system control circuit 90.The fuel cell system control circuit 90 drives the purge valve 83 toeffect purge, and discharges excessive moisture and impurities in thefuel cell stack 81 to the external of the electronic camera main body100 via the exhaust port 96. During purge, in order to maintain thehydrogen pressure in the fuel cell stack 81 at a predetermined value,hydrogen is always exhausted from the hydrogen absorbing alloy 410 inthe fuel tank 400 and sent to the fuel cell 80 via the connectors 93 and412 (Step S404). After purge, the system control circuit 50 stopsdriving the fuel cell 80 and stops an electric power supply to theelectronic camera main body 100.

If the single-lens reflex digital camera has the power saving mode, thepower saving mode state may occur after the lapse of the predeterminedtime. In this case, purge is effected in the power saving mode. Whetherthe system control circuit 50 outputs the purge start signal to the fuelcell system control circuit 90 in YES at Step S403, may be determinedbased on the following fact. As described with Steps S101 and S102 inFIG. 3, the cell voltage detection circuit 89 measures the cell voltageof the fuel cell stack 81, and in accordance with this measurement, thefuel cell system control circuit 90 notifies the system control circuitof that purge is necessary, or not.

As described above, according to the single-lens reflex digital cameraof this embodiment, even if the fuel gas of the fuel electrode in thefuel cell 80 is reduced because the single-lens reflex digital camera ismaintained unused for a long time, purge is effected before autopower-off. It is therefore possible to fill the fuel electrode with fuelgas. It is possible to improve a rise of the output voltage of the fuelcell 80 when the electronic camera main body 100 is activated next.

Fourth Use State

The single-lens reflex digital camera is activated again in the forthuse state that the fuel gas of the fuel electrode in the fuel cell 80was reduced because the single-lens reflex digital camera was maintainedunused for a long time and the fuel cell 80 was not driven, and in theauto power-off state. FIG. 8 is a flow chart illustrating an example ofthe control operation for the fuel cell 80 of the single-lens reflexdigital camera in the fourth use state.

As shown in FIG. 8, first the system control circuit 50 judges whetherthe electric power switch 72 is turned on (Step S501). If it is judgedthat the electric power switch 72 is turned on (YES at Step S501), thesystem control circuit 50 starts driving the fuel cell 80 to activatethe single-lens reflex digital camera (Step S502). If it is judged thatthe electric power switch 72 is in an OFF state (NO at Step S501), thesystem control circuit 50 repeats the judgment process until theelectric power switch 72 is turned on. In the state that the electricpower switch 72 is OFF, an electric power is not supplied to thesingle-lens reflex digital camera, so that the judgment process is notperformed. When the electric power switch 72 changes from the OFF stateto an ON state, an electric power is supplied to the system controlcircuit 50 to judge the state of the electric power switch.

Next, after the single-lens reflex digital camera is activated, thesystem control circuit 50 controls the timing generator circuit 18 tomeasure the time from when various switches of the operation unit 70 andthe like are lastly operated to the present time, to thereby judgewhether the camera unoperated state reaches a predetermined time (StepS503).

If it is judged at Step S503 that the camera unoperated time does notreach the predetermined time (NO at Step S503), the system controlcircuit 50 repetitively measures the time from when various switches ofthe operation unit 70 and the like are lastly operated to the presenttime, until it is judged that the camera unoperated state is longer thanthe predetermined time.

If it is judged at Step S503 that the camera unoperated state reachesthe predetermined time (YES at Step S503), the system control circuit 50stops a main electric power supply for driving the electronic cameramain body 100 (Step S504). In this case, even if the main electric powersupply for driving the electronic camera main body 100 is stopped, anelectric power supply to the system control circuit 50 continues, forexample, from the electric power supply unit 116. Next, the systemcontrol circuit 50 judges whether various operation switches of theoperation unit 70 and the like are operated (whether the cameraunoperated state terminates) (Step S505).

If it is judged that the camera unoperated state continues (NO at StepS505), the judgment process is repeated until various operation switchesof the operation unit 70 and the like are operated again. If it isjudged at Step S505 that the operation of various operation switches ofthe operation unit 70 and the like is detected (YES at Step S505), thesystem control circuit 50 controls the electric power source controlcircuit 98 to stop driving the fuel cell 80, and controls the electricpower source change-over unit 97 to change the electric power source ofthe electronic camera main body 100 from the fuel cell 80 to the powersource unit 116 and start a power supply to the electronic camera mainbody 100 (Step S506).

Next, the system control circuit 50 outputs a purge start signal to thefuel cell system control circuit 90. The fuel cell system controlcircuit 90 drives the purge valve 83 to effect purge; and dischargesexcessive moisture and impurities in the fuel cell stack 81 to theexternal of the electronic camera main body 100 via the exhaust port 96.During purge, in order to maintain the hydrogen pressure in the fuelcell stack 81 at a predetermined value, hydrogen is always exhaustedfrom the hydrogen absorbing alloy 410 in the fuel tank 400 and sent tothe fuel cell 80 via the connectors 93 and 412 (Step S507). After purge,the system control circuit 50 controls the electric power sourcechange-over unit 97 to change the electric power source of theelectronic camera main body 100 from the electric power source unit 116to the fuel cell 80 (Step S508).

In the sequence from Step S506 to S507, whether the system controlcircuit 50 outputs the purge start signal to the fuel cell systemcontrol circuit 90, may be determined based on the following fact. Asdescribed with Steps S101 and S102 in FIG. 3, the cell voltage detectioncircuit 89 measures the cell voltage of the fuel cell stack 81, and inaccordance with this measurement, the fuel cell system control circuit90 notifies the system control circuit of that purge is necessary, ornot.

As described above, according to the single-lens reflex digital cameraof this embodiment, purge of the fuel cell 80 can be effected when thesingle-lens reflex digital camera is activated again in the state thatthe fuel gas of the fuel electrode in the fuel cell 80 was reducedbecause the single-lens reflex digital camera was maintained unused fora long time and the fuel cell 80 was not driven, and in the autopower-off state. Since the fuel electrode of the fuel cell 80 is filledwith fuel gas, it is possible to improve a rise of the output voltage ofthe fuel cell 80 when the electronic camera main body is re-activated.Since the electric power source unit 116 is used in place of the fuelcell 80 during purge, driving the electronic camera main body can becontinued without influencing the operation thereof even if the outputvoltage of the fuel cell 80 lowers during purge.

Fifth Use State

Purge is effected in the fifth use state when a user of the single-lensreflex digital camera turns on the purge operation switch 78. FIG. 9 isa flow chart illustrating an example of the control operation for thefuel cell 80 of the single-lens reflex digital camera in the fifth usestate.

As shown in FIG. 9, first the system control circuit 50 judges whetherthe electric power switch 72 is turned on (Step S601). If it is judgedthat the electric power switch 72 is turned on (YES at Step S601), thesystem control circuit 50 starts driving the fuel cell 80 to activatethe single-lens reflex digital camera (Step S602). If it is judged thatthe electric power switch 72 is in an OFF state (NO at Step S601), thesystem control circuit 50 repeats the judgment process until theelectric power switch 72 is turned on. In the state that the electricpower switch 72 is OFF, an electric power is not supplied to thesingle-lens reflex digital camera, so that the judgment process is notperformed. When the electric power switch 72 changes from the OFF stateto an ON state, an electric power is supplied to the system controlcircuit 50 to judge the state of the electric power switch.

After the single-lens reflex digital camera is activated at Step S602,the system control circuit 50 controls the timing generator circuit 18to measure the time from when the single-lens reflex digital camera isactivated to the present time, to thereby judge whether a predeterminedtime reaches (Step S603). If it is judged at Step S603 that the timefrom when the single-lens reflex digital camera is activated to thepresent time does not reach the predetermined time (NO at Step S603),the system control circuit 50 repetitively measures the time from whenthe single-lens reflex digital camera is activated to the present time,until the time exceeds the predetermined time.

If it is judged at Step S603 that the time from when the single-lensreflex digital camera is activated to the present time, reaches thepredetermined time (YES at Step S603), the system control circuit 50controls the purge alarm unit 55 to issue an alarm to a user of thesingle-lens reflex digital camera and make the user turn on the purgeoperation switch 78.

Next, the system control circuit 50 judges whether the user turns on thepurge operation switch (Step S605). If it is judged that the purgeoperation switch 78 is not turned on (NO at Step S605), the systemcontrol circuit 50 instructs the purge alarm unit 55 to continuouslyissue the alarm, and repetitively judges whether the purge operationswitch 78 is turned on.

If it is judged at Step S605 that the user turns on the purge operationswitch 78 in response to the alarm from the purge alarm unit 55 (YES atStep S605), the system control circuit 50 controls the electric powersource change-over unit 97 to change the electric power source of theelectronic camera main body 100 from the fuel cell 80 to the powersource unit 116.

Next, the system control circuit 50 outputs a purge start signal to thefuel cell system control circuit 90. The fuel cell system controlcircuit 90 drives the purge valve 83 to effect purge, and dischargesexcessive moisture and impurities in the fuel cell stack 81 to theexternal of the electronic camera main body 100 via the exhaust port 96.During purge, in order to maintain the hydrogen pressure in the fuelcell stack 81 at a predetermined value, hydrogen is always exhaustedfrom the hydrogen absorbing alloy 410 in the fuel tank 400 and sent tothe fuel cell 80 via the connectors 93 and 412 (Step S607).

After purge, the system control circuit 50 controls the electric powersource change-over unit 97 to change the electric power source of theelectronic camera main body 100 from the electric power source unit 116to the fuel cell 80 (Step S608).

Next, the system control circuit 50 controls the timing generatorcircuit 18 to measure the time from a purge completion to the presenttime and judge whether the time reaches a predetermined time (StepS609).

If it is judged at Step S609 that the time from the purge completion tothe present time does not reach the predetermined time (NO at StepS609), the system control circuit 50 repetitively measures the time fromthe purge completion to the present time, until the time excesses thepredetermined time. If it is judged at Step S609 that the time from thepurge completion to the present time reaches the predetermined time (YESat Step S609), the flow returns to Step S604.

When an alarm is issued at Step S604, whether the alarm is to be issuedmay be judged in the following manner. The cell voltage detectioncircuit 89 measures the cell voltage of the fuel cell stack 81, and inaccordance with the measurement result, the fuel cell system controlcircuit 90 notifies the system control circuit of a necessity of purge.Namely, when it is judged that purge is not necessary, the alarm may notbe issued.

As described above, according to the single-lens reflex digital cameraof this embodiment, purge is effected when a user of the single-lensreflex digital camera turns on the purge operation switch 78. It istherefore possible to continuously use the single-lens reflex digitalcamera, without being bothered with a voltage drop during purge orimpact by purge (depending upon the position of a hand or a face of theuser, there is a possibility that the user receives impact such as beingsurprised by discharge from the exhaust port 96 during purge).

A timing when purge is necessary is judged from a continuous drive timeof the single-lens reflex digital camera. It is therefore possible tonotify a user of the single-lens reflex digital camera of a timing whenthe purge operation switch 78 is depressed. Since the electric powersource unit is used in place of the fuel cell 80 during purge, shortageof the fuel cell of the single-lens reflex digital camera to be causedby a voltage drop during purge can be prevented, and driving theelectronic camera main body can be continued without influencing theoperation thereof.

Another Operation in Fifth Use State

Description will be made on an example of the operation different fromthe operation shown in FIG. 9 in the fifth use state.

FIG. 10 is a flow chart illustrating another example of the controloperation for the fuel cell 80 of the single-lens reflex digital camerain the fifth use state. The processes at Steps S701 and S702 and theprocesses at Steps S704 to S707 shown in FIG. 10 are similar to theprocesses at Steps S601 and S602 and the processes at Steps S604 to S607shown in FIG. 9, and the description thereof is omitted.

After the single-lens reflex digital camera is activated at Step S702,the fuel cell system control circuit 90 makes the cell voltage detectioncircuit 89 measure the cell voltage of the fuel cell stack 81 to therebyjudge whether the cell voltage is lower than a predetermined value(whether purge is necessary) (Step S703).

If it is judged that the cell voltage is higher than the predeterminedvalue (NO at Step S703), the cell voltage detection circuit 89 measuresagain the cell voltage of the fuel cell stack 81, and the process atStep S703 is repeated until the cell voltage becomes lower than thepredetermined value. If it is judged that the cell voltage is lower thanthe predetermined value (YES at Step S703), the fuel cell system controlcircuit 90 notifies the system control circuit 50 of a necessity ofpurge. The system control circuit 50 controls the purge alarm unit 55 toissue an alarm to a user to make the user turn on the purge operationswitch 78 (Step S704).

After purge is completed at Step S707, the system control circuit 50controls the electric power source change-over circuit 97 to change theelectric power source of the electronic camera main body 100 from theelectric power source unit 116 to the fuel cell 80 (Step S708) tothereafter return to Step S703.

As described above, according to the single-lens reflex digital cameraof this embodiment, purge is effected when a user of the single-lensreflex digital camera turns on the purge operation switch 78, and thesingle-lens reflex digital camera can be continuously used without beingbothered with a voltage drop during purge or impact to be caused bypurge.

Further, a timing when a purge operation switch is depressed can benotified to a user of the single-lens reflex digital camera, by judgingfrom the output voltage of the fuel cell 80 the timing when purgebecomes necessary and issuing an alarm when purge becomes necessary.Furthermore, since the electric power source unit 116 is used in placeof the fuel cell 80 during purge, shortage of the fuel cell of thesingle-lens reflex digital camera to be caused by a voltage drop duringpurge can be prevented, and driving the electronic camera main body bythe fuel cell 80 can be continued without influencing the operationthereof.

In the above-described embodiments, the fuel cell 80 is loaded in theelectronic camera main body 100 and the fuel tank 400 is detachablyloaded in the electronic camera main body 100. This is an example ofpreferred embodiments of the present invention, and the presentinvention is not limited thereto. For example, the fuel cell 80 togetherwith the fuel tank 400 may be mounted in the external of the electroniccamera main body 100, and connected to the electronic camera main body100 via the connectors 93 and 412. In this case, electric power sourcelines for supplying an electric power source voltage are provided, andsignal lines for transferring signals between the system control circuit50 and fuel cell system control circuit 90 are provided.

As described so far, according to the single-lens reflex digital cameraof the embodiments, purge is effected in accordance with the camerastate. It is therefore possible to effect purge of the fuel cell 80 atthe timing not influencing the camera operation, and driving the fuelcell 80 can be continued. According to the single-lens reflex digitalcamera of the embodiments, since purge is effected in the cameraoperation sequence at the timing when a consumption power is small,battery shortage or the like of the single-lens reflex digital camera tobe caused by a voltage drop during purge can be presented.

Further, according to the single-lens reflex digital camera of theembodiments, even in the state that the fuel gas of the fuel electrodein the fuel cell 80 was reduced because the single-lens reflex digitalcamera was maintained unused for a long time and the fuel cell 80 wasnot driven, since purge is effected when the electric power switch 72 ofthe single-lens reflex digital camera is turned on, and then the fuelelectrode of the fuel cell 80 is filled with fuel gas, it is possible toimprove a rise of the output voltage.

The embodiments of the present invention have been described in detailwith reference to the accompanying drawings. Specific structures are notlimited to the embodiments, but other designs and the like are possiblein the range not departing from the gist of the present invention.

According to the embodiments of the present invention, a single-lensreflex digital camera is used as an example of the electronic apparatusof the present invention. The electronic apparatus of the presentinvention is not limited only to the single-lens reflex digital camera,but other compact electronic apparatus may also be used, such as acompact camera, a PDA, a mobile phone and a note type personal computer.

Next, description will be made on a portable electronic apparatusadopting the present invention, by using a cellar phone as an example.

FIGS. 13A and 13B are block diagrams showing the internal structure of acellar phone according to an embodiment of the present invention. A fuelcell 80 and a fuel tank 400 are represented by identical referencenumerals to those of the corresponding components in FIGS. 1A and 1B forthe convenience of description.

As shown in FIGS. 13A and 13B, the cellar phone of the embodiment isconstituted of a cellar phone main body 500, a fuel tank (hydrogensupply source) 400, an electric power source unit 600 and a fuel cellunit 700. The fuel tank 400 and electric power source unit 600 aredetachably mounted on the cellar phone main body 500.

A cellar phone system control circuit 510 has a central processing unit(CPU), an internal random access memory (internal RAM), a read-onlymemory (ROM) and the like (each of them is not shown). The CPU controlsthe entirety of the cellar phone main body 500 by using a predeterminedarea of the internal RAM as a working area, in accordance with variouscontrol programs stored in ROM.

A storage unit 512 is a volatile memory RAM, a magnetic/opticalrecording medium and its reader unit, or a non-volatile memory. Forexample, the storage unit stores programs for the system and operationof the cellar phone main body 500, including an operating system (OS)and various operation programs, and various data such as moving imagesand audio data.

A display driver 520 converts an image signal input from the cellarphone system control circuit 510 into an image output signal which isoutput to a main display unit 522 or sub-display unit 524 to display animage.

An operation unit 530 is made of various buttons, touch panels and thelike.

A speaker 532 outputs sounds and voices in accordance with audio outputdata input from the cellar phone system control circuit 510.

A microphone 534 converts externally-input sounds and voices into anaudio analog signal and outputs the signal to the cellar phone systemcontrol circuit 510.

An electric power switch 536 can selectively set each of electric poweron/off modes of the cellar phone main body 500.

A drive power detection circuit 538 detects a drive electric power ofthe cellar phone main body 500.

A fuel run-out warning unit 540 warns a user about the fact thathydrogen is required to be supplied immediately to hydrogen absorbingalloys 410 if the hydrogen remaining amount in the hydrogen absorbingalloys 410 of the fuel tank 400 becomes lower than a predeterminedamount necessary for driving the cellar phone, or the fact that a fueltank 400 having hydrogen absorbing alloys 410 absorbing hydrogensufficient for driving the cellar phone is required to be attached tothe fuel cell unit 700.

An electric power source change-over unit 542 switches the electricpower source of the cellar phone main body 500 from the fuel cell unit700 to the electric power source unit 600, or from the electric powersource unit 600 to the fuel cell unit 700, under the control of thecellar phone system control circuit 510.

An electric power source control circuit 544 is constituted of a celldetection circuit, a DC-DC converter, a switch circuit for switching ablock to be powered. The electric power source control circuit detectsthe type of a cell and a cell remaining amount, and controls the DC/DCconverter in accordance with the detection results or an instructionfrom the cellar phone system control circuit 510 to thereby supply anecessary voltage to each component for a necessary period.

Connectors 546 and 604 interconnect the cellar phone main body 500 andelectric power source unit 600.

Connectors 548 and 706 interconnect the cellar phone main body 500 andfuel cell unit 700.

An image entered from a photographing lens 554 and focused on an imagepickup element 552 is converted into an image signal which is output tothe cellar phone system control circuit 510, in accordance with aninstruction from the cellar phone system control circuit 510.

A communication antenna 562 transmits and receives a reception signaland a reception signal which are subjected to an RF process by awireless transmission unit 564.

A transmission/reception change-over switch 566 is connected to areception or transmission side by the cellar phone system controlcircuit 510.

Reference numeral 568 denotes a receiving unit, reference numeral 570denotes a received data processing unit, reference numeral 572 denotes atransmission unit, and reference numeral 574 denotes a transmission dataprocessing unit.

In a reception mode, under the control of the cellar phone systemcontrol circuit 510, the change-over switch 566 is first connected tothe side of the receiving unit 568. A signal received at thecommunication antenna 562 is subjected to the RF process at the wirelesstransmission unit 564, thereafter demodulated at the receiving unit 568,and then decoded at the received data processing unit 570.

If the signal is audio data, it is output from the speaker 532, whereasif the signal is text data or image data, it is displayed on the maindisplay unit 522 or sub-display unit 524 via the display driver 520.

In a transmission mode, under the control of the cellar phone systemcontrol circuit 510, the change-over switch 566 is connected to the sideof the transmission unit 572. Data input from the operation unit 530,microphone 534 or image pickup element 552 is input to the transmissiondata processing unit 574, encoded at the transmission data processingunit 574, modulated at the transmission unit 572, subjected to the RFprocess at the wireless transmission unit 564, and then transmitted fromthe communication antenna 562.

Next, the electric power source unit 600 will be described. The electricpower source unit 600 is constituted of an electric power source 602 anda connector 604. The electric power source 602 is constituted of aprimary battery such as an alkali battery and a lithium battery, asecondary battery such as a NiCd battery, an NiMH battery and a Libattery, and an AC adapter. The connector 604 interconnects the electricpower source unit 600 and cellar phone main body 500.

Next, the fuel cell unit 700 will be described. The fuel cell unit 700is constituted of a fuel cell unit 80, a fuel remaining amount detectionunit 702, a fuel tank attach and detach detection unit 704, connectors706 and 708, a gas inlet port 710 and a gas outlet port 712. In thecellar phone of the embodiment, the fuel cell unit 700 is detachablymounted on the cellar phone main body 500, and the fuel tank 400 isdetachably mounted on the fuel cell unit 700.

The fuel remaining amount detection unit 702 detects a fuel remainingamount in the fuel tank 400 connected to the fuel cell unit 700 via theconnectors 706 and 412, i.e., detects a hydrogen remaining amount in thehydrogen absorbing alloys 410.

A fuel tank attach and detach detection unit 704 detects whether thefuel tank 400 is mounted on the connector 708.

The connector 7046 interconnects the cellar phone main body 500 and fuelcell unit 700, and the connector 708 interconnects the fuel cell unit700 and fuel tank 400. The gas inlet port 710 is used for supplying airto an oxygen electrode (not shown) of the fuel cell 80. The gas outletport 712 is used for exhausting hydrogen, impurities and air used by thefuel cell 80 during purge of the fuel cell 80 to an external of thecellar phone main body 500.

Next, description will be made on a purge control operation of thecellar phone shown in FIGS. 13A and 13B.

FIG. 14 is a flow chart illustrating a purge control operation of thecellar phone shown in FIGS. 13A and 13B. First, while the cellar phonemain body 500 is driven by using the fuel cell 80 as an electric powersource unit, the fuel cell system control circuit 90 makes the cellvoltage detection circuit 89 measure a cell voltages of a fuel cellstack 81, and judges whether the cell voltage is lower than a firstpredetermined value at which purge is required (Step S801).

If it is judged that the cell voltage is higher than the firstpredetermined value (No at Step S801), the fuel cell system controlcircuit 90 returns to Step S801 to make the cell voltage detectioncircuit 89 measure a cell voltage of the fuel cell stack 81 and repeatStep S801 until the cell voltage becomes lower than the firstpredetermined value.

If it is judged that the cell voltage is lower than the firstpredetermined value (YES at Step S801), the fuel cell system controlcircuit 90 controls the fuel remaining amount detection unit 702 todetect a hydrogen remaining amount in the hydrogen absorbing alloys 410and judge whether a sufficient amount of hydrogen for abrupt hydrogenemission by purge remains in the hydrogen absorbing alloys 410 (StepS802).

If the hydrogen remaining amount in the hydrogen absorbing alloys 410 isinsufficient for purge (NO at Step S802), the flow advances to StepS804. The operation at Step S804 and following Steps will be describedlater with reference to FIG. 15.

If a hydrogen remaining amount in the hydrogen absorbing alloys 410 isinsufficient for purge (YES at Step S802), the fuel cell system controlcircuit 90 transmits a purge permission signal to the cellar phonesystem control circuit 510 via the connectors 548 and 704 (Step S803).

Next, the cellar phone system control circuit 510 judges whetherimpurity exhaust by purge of the fuel cell unit 700 does not influenceuse of the cellar phone main body 500 (Step S805). For example, if thecellar phone main body 500 is photographing with the image pickupelement 552 and purge is performed, there arises a possibility of handshaking to be caused by vibrations during impurity exhaust. If thecellar phone main body 500 is picking up external sounds and voices fromthe microphone 534, there is a possibility that sounds during impurityexhaust by purge are picked up by to the microphone.

If it is judged at Step S805 that the operation state of the cellarphone main body 500 is not influenced by purge of the fuel cell unit 700(YES at Step S805), the cellar phone system control circuit 510 controlsthe drive electric power detection unit 530 to judge whether a driveelectric power of the cellar phone main body 500 has a level notinfluenced by a temporary voltage drop by purge (Step S806).

If it is judged at Step S805 that the operation state of the cellarphone main body 500 is influenced by purge of the fuel cell unit 700 (NOat Step S805), the fuel cell system control circuit 90 makes the cellvoltage detection circuit 89 measure a cell voltage of the fuel cellstack 81, and judges whether a cell voltage is lower than a secondpredetermined value necessary for driving the cellar phone main body 500(Step S807). If the cell voltage of the fuel cell stack 81 is higherthan the second predetermined value (NO at Step S807), the flow returnsto Step S805.

If the cell voltage of the fuel cell stack 81 is lower than the secondpredetermined value capable of driving the cellar phone main body 500(YES at Step S807), the cellar phone system control circuit 510 controlsthe electric power change-over unit 542 to change the electric powersource of the cellar phone main body 500 from the fuel cell unit 700 tothe electric power source unit 600, to thereby supply an electric powerto each component of the cellar phone main body 500 from the electricpower source 602 via the connectors 546 and 604 (Step S808).

Next, the cellar phone system control circuit 510 judges whetherimpurity exhaust by purge of the fuel cell unit 700 does not influenceuse of the cellar phone main body 500 (Step S809).

If it is judged at Step S809 that impurity exhaust by purge of the fuelcell unit 700 does not influence use of the cellar phone main body 500(YES at Step S809), the flow advances to Step S813.

If it is judged at Step S809 that impurity exhaust by purge of the fuelcell unit 700 influences use of the cellar phone main body 500 (NO atStep S809), judgment is repeated until the operation state of the cellarphone main body 500 enters the state wherein purge can be performed.

If it is judged at Step S806 that a drive electric power of the cellarphone main body 500 has a level not influenced by a temporary voltagedrop by purge (YES at Step S806), the cellar phone system controlcircuit 510 transmits a purge permission signal to the fuel cell systemcontrol circuit 90 via the connectors 548 and 704 (Step S810).

Upon reception of the purge permission signal from the cellar phonesystem control circuit 510, the fuel cell system control circuit 90controls a purge valve 83 to exhaust excessive water and impurities inthe fuel cell stack to the external of the fuel cell unit 700 via thegas outlet port 710 (Step S811).

If it is judged at Step S806 that a drive electric power of the cellarphone main body 500 has a level influenced by a voltage drop by purge(NO at Step S806), the cellar phone system control circuit 510 controlsthe electric power change-over unit 542 to change over the electricpower source of the cellar phone main body 500 from the fuel cell unit700 to the electric power source unit 600 to supply an electric power toeach component of the cellar phone main body 500 from the electric powersource 602 via the connectors 546 and 604 (Step S812).

Next, the cellar phone system control circuit 510 transmits a purgepermission signal to the fuel cell system control circuit 90 via theconnectors 548 and 706 (Step S813). The fuel cell system control circuit90 received the purge permission signal drives the purge valve 80 toeffect purge and exhaust excessive water and impurities in the fuel cellstack to the external of the fuel cell unit 700 via the gas outlet port710 (Step S814).

After the purge is completed, the fuel cell system control circuit 90transmits a purge completion notice signal to the cellar phone systemcontrol circuit 510 via the connectors 548 and 706 (Step S815).

Upon reception of the purge completion notice signal from the fuel cellsystem control circuit 90, the cellar phone system control circuit 510controls the electric power change-over unit 542 to change over theelectric power source of the cellar phone main body 500 from theelectric power source unit 600 to the fuel cell unit 700 (Step S816).

FIG. 15 is a flow chart illustrating the operation to be executed if itis judged at Step S802 shown in FIG. 14 that a sufficient amount ofhydrogen for abrupt hydrogen emission by purge does not exist in thehydrogen absorbing alloys 410 in the fuel tank 400.

At Step S802 shown in FIG. 14, the fuel cell system control circuit 90controls the fuel remaining amount detection unit 702 to detect ahydrogen remaining amount in the hydrogen absorbing alloys 410 and judgewhether a sufficient amount of hydrogen for abrupt hydrogen emission bypurge exists in the hydrogen absorbing alloys 410 in the fuel tank 400.If the hydrogen remaining amount in the hydrogen absorbing alloys 410 isinsufficient for hydrogen emission by purge (NO at Step S802), the fuelcell system control circuit 90 transmits an electric power change-overrequest signal to the cellar phone system control circuit 510 via theconnectors 548 and 706 to change over the electric power source of thecellar phone main body 500 from the fuel cell unit 700 to the electricpower source unit 600 (Step S901).

Upon reception of the electric power change-over signal from the fuelcell system control circuit 90, the cellar phone system control circuit510 controls the electric power source change-over unit 542 to changeover the electric power source of the cellar phone main body 500 fromthe fuel cell unit 700 to the electric power source unit 600 and supplyan electric power to each component of the cellar phone main body 500from the electric power source 602 via the connectors 546 and 604 (StepS902).

Next, the cellar phone system control circuit 510 controls the fuelrun-out warning unit 540 to warn the cellar phone user about the factthat hydrogen sufficient for driving the cellar phone does not exist inthe hydrogen absorbing alloys 410 of the fuel tank 400 (Step S903).

As described above, according to the cellar phone of the embodiment,when an output voltage of the fuel cell unit 700 lowers and it becomesnecessary to perform purge, a purge permission signal is transmitted tothe cellar phone system control circuit 510. When purge is completed, apurge completion notice signal is transmitted. If the hydrogen remainingamount in the hydrogen absorbing alloys 410 is smaller than an amountnecessary for purge, an electric power source change-over request signalis transmitted. In this manner, the cellar phone system control circuit510 can grasp the operation state of the fuel cell unit 700.

Upon reception of the purge permission signal request signal from thefuel cell unit 700, the cellar phone system control circuit 510transmits the purge permission signal to the fuel cell system controlcircuit 90 in accordance with the drive state of the cellar phone mainbody 500. Accordingly, the cellar phone can be used continuously,without being bothered about purge impacts (there is a possibility thata user receives impacts such as gas exhaust from the gas outlet port 710by purge).

Further, if the cellar phone main body 500 cannot bear a temporaryvoltage drop by purge, a supply electric power source of the cellarphone main body 500 is changed over from the fuel cell unit 700 to theelectric power source unit 600. It is therefore possible to prevent abattery run-out of the cellar phone main body 500 to be caused by avoltage drop during purge, and to continue driving by the fuel cell unit700 without influencing the operation of the cellar phone.

Each means shown in FIGS. 1A, 1B and 2 constituting the single-lensreflex digital camera of the above-described embodiments and each stepshown in FIG. 3 and FIGS. 5, 6, 7, 8, 9 and 10 illustrating a controlmethod for the single-lens reflex digital camera, can be realized byrunning a program stored in a RAM or ROM of a computer. The presentinvention includes this program and a computer readable recording mediumstoring this program.

More specifically, the program is supplied to a computer in the form ofa recording medium such as a CD-ROM or via various transmission media.The recording medium for recording the program includes in addition toCD-ROM, a flexible disc, a hard disc, a magnetic tape, a magneto opticaldisc, a non-volatile memory card and the like. The transmission mediafor the program may be communication media (wired lines such as opticalfibers, wireless lines and the like) in a computer network (LAN, WANsuch as the Internet, wireless communication networks and the like) forsupplying program information by using carriers.

The present invention also includes other program types. Namely, thefunctions of the single-lens reflex digital camera of the embodimentsare realized by running a program supplied to the computer, thefunctions of the single-lens reflex digital camera of the embodimentsare realized by running the program in corporation with an operatingsystem (OS) running in the computer or other application software, orthe functions of the single-lens reflex digital camera of theembodiments are realized by making a function expansion board or afunction expansion unit of a computer execute all or part of theprocesses of the supplied program.

This application claims priority from Japanese Patent Application No.2005-140840 filed on May 13, 2005, which is hereby incorporated byreference herein.

1. A fuel cell device supplying electric power with an electronicapparatus which can detect a consumption power of the electronicapparatus, comprising: an electric power output unit for outputting anelectric power through a chemical reaction between fuel gas and oxidantgas; a purge unit device for purging the electric power output unit; anda purge control unit for outputting a purge instruction to the purgedevice, in accordance with the consumption power detected by theelectronic apparatus.
 2. The fuel cell unit according to claim 1,wherein the purge control unit requests the electronic apparatus about apurge execution permission.
 3. The fuel cell unit according to claim 2,wherein the purge execution permission is requested when an outputvoltage of the electric power output unit becomes lower.